Flashlight lamp



y 1941- HANS-JOACHIM HELWIG arm. 2,248,670

FLASHLIGHT LAMP Filed Ju1y'20, 1937 IIIMVENORS Hans-Joachim Helwig MaxMcetschke A TORNEY Patented July 8, 1941 anam- FLASHLIGHT LAM]?Hans-Joachim Helwig, Berlin-Schoneberg, and

Max Maetschke, Berlin-Charlottenburg, Germany, assignors toGeneral-Electric Company, a corporation of New York Application July 20,1937, Serial No. 154,676 In Germany July 28, 1936 2 Claims.

Our invention relates to evacuated devices comprising a sealed envelopeor vessel containing a gaseous atmosphere at a pressure considerablybelow atmospheric, and more particularly to flash light lamps, mainlyfor photographic purposes, containing one or more light-developingcombustible metal strips or foils, for instance of aluminium ormagnesium, in a sealed vessel similar to the bulb of an incandescentlamp, which vessel contains oxygen at a pressure far below atmospheric;instead of the metal strip or foil metallic powder or a clue of metalwire may be used as well. This flash material is ignited by electricmeans.

Flash light lamps of this type have the drawback that, as soon as airhas entered the bulb due to a crack, the lamp has a tendency to burstwhen being ignited. Therefore it already has been proposed to arrangeinside the vessel a capillary tube filled with a small amount of air andclosed by a drop of mercury, so that, provided the pressure of theoxygen is correct, the air enclosed in the capillary tube expands and,by moving the drop of mercury, causes a connection between twointerrupted ends of the igniting wire; on the other side, if air hasentered the vessel from outside, the drop of mercury moves to theopposite direction, leaving the two interrupted ends of the ignitingwire unconnected, so that the lamp cannot be ignited.

This arrangement, acting as an indicating and a safe-guarding means atthe same time, has the disadvantage of being manufactured only in arather complicated way and of not acting with.

the certainty wanted, due to the tendency of the mercury to adhere tothe Walls of the capillary tube or, even, to move in a way not wanted onaccount of the lamp being shaken by transport or by handling it.

The object of our invention is to provide a simple apparatus forevacuated devices such as flash light lamps, indicating the correctpressure of the gas-filling and not aiiected by shocks or similarinfluences.

According to the invention this indicating arrangement consists of ahollow body, preferably shaped like a ball, whose walls are formed by anelastic material, the body containing air at a pressure somewhat higherthan the pressure inside the lamp-vessel, but lower than atmosphericpressure. Also, an elastic body of this kind is blown up as long as thegas-pressure of the bulb is correct and unchanged, but is compressed ifair has entered the bulb due to a crack.

In the drawing accompanying this specification: The Figure 1 shows, inelevation, a typical flash light lamp, the Figures 2 and 3 show thebottom parts of two similar lamps but of a slightly different kind. Theprincipal parts of the three lamps are constructed in the normal way.

The bulb l, as Figure 1 shows, is provided with a stem 2, lead-in wires3-4, and an exhausting pipe 5. An igniting wire 6, carrying an igniter6' of the known type, is fixed to the free ends of the leading-in wiresinside the bulb l. Furthermore, the bulb l contains a flash materialsuch as aluminium foil I, and a filling of oxygen at a pres sure belowatmospheric, for instance 200 mm. of mercury. The upper part 8 of theexhausting pipe 5 extends far above the pinch 9 of the stem 2. Thus, thelower end of the part 8 is closed by the pinch, while the upper end isopen. A ballshaped body In of an elastic material, such as rubber,pressed together as it is, is placed upon the upper end of the tube,yielding an airtight closing against the bulb. As soon as the bulb I hasbeen evacuated and filled with the proper amount of oxygen, thecompressed elastic body it] swells due to the air contained in the pipe8. Thus a safe indication that the pressure inside the bulb is below oneatmosphere and no air has entered the bulb is obtained. If, on thecontrary, air has got into the bulb, the elastic body If), again, ispressed together, thus indicating by its shape being altered that thelamp must not be used.

It is not by all means, necessary that the elastic body 10 be placed onthe top of a pipe. It may just as well, as is shown in Figure 2, bearranged as a closed ball filled with attenuated air, inside the neck l2of the bulb l.

According to Figure 3 the elastic body, too, may have the shape of abellows 13 consisting of any elastic material, preferably of a very thinelastic metal sheet. Preferably, the bellows I3 is fixed to the stem 2of the lamp by means of a clip l4.

What we claim as new and desire to secure by Letters Patent oi theUnited States is:

1. A flash light lamp comprising a closed transparent vessel containinga combustible material, oxygen at a pressure below atmospheric, anigniter and a hollow rubber ball whose fillingpressure is somewhathigher than the correct pressure of the lamp, but lower than atmosphericpressure, the rubber ball being placed upon and having its interiorcommunicating with the open end of a pipe whose other end is sealedairtight to a part of the interior of the vessel, so that the rubberball blows up if the filling pressure of the pressure of the lamp, butlower than atmospheric pressure, the rubber ball being placed upon andhaving its interior communicating with the open end of a pipe whoseother end is sealed airtight to the pinch of the vessel whereby saidball is normally expanded but is compressed upon leakage of air into thevessel.

HANS-JOACHIM HELVVIG. MAX MAETSCHKE.

